Method and apparatus for rebound control

ABSTRACT

A stabilizing apparatus and method that replaces the existing shock absorber of a road vehicle that works to resist the initiation of body roll during cornering. It seeks to counter act the forces being generated by the vehicle suspension springs that exacerbate the rollover propensity of vehicles during certain steering maneuvers.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to:

U.S. Ser. No. 09/803,505 filed on Mar. 9, 2001 entitled Opposing SpringResilient Tension Suspension System.

U.S. Ser. No. 10/033,016 filed on Oct. 26, 2001 entitled Opposing SpringRebound Tension Suspension System.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

REFERENCE TO A “MICROFICHE APPENDIX”

Not Applicable

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to and, in particular, to improvements inthe methods and apparatus for using a rebound spring carried on a shockabsorber that is intended to utilize the unsprung weight of thewheel/axle system during rebound. More particularly, it is to resistrollover, sway, yaw and other chassis motion.

2. Description of Related Art Including Information Disclosed Under 37CFR 1.97 and 1.98

In the past ten years the numbers of sport utility vehicles “SUV” andpickup trucks have increased dramatically to the point where thosevehicles are more popular than the millions of passenger cars on theroad. The SUV and trucks inherently have a higher center of gravity (CG)than normal passenger cars due to the need for higher ground clearancefor bad weather travel (snow and ice), off-road use and/or for pickuptruck payloads. Vehicles with a higher CG have a greater propensity tosway or even rollover during abrupt lane changes and evasive steeringmaneuvers than the lower normal passenger cars.

One important arrangement of all these vehicles is the method ofsuspension used. Except for the use of hydraulic shock absorber dampingresistance to rebound, all vehicle chassis and body loads are supportedon the vehicle axles with various types of suspensions that have springsthat resist primarily load and jounce of each wheel axle. No existingsuspensions using coil springs, load leaf springs, air springs, torsionbars or rubber blocks suspensions have any other provision for reboundcontrol of the forces due to inertia or gravity type negative suspensionloads. Particularly, those rebound forces occurring at the inside wheelduring hard cornering or if a wheel drops into a pothole.

Typically, changes in suspension loads while driving straight along aroad are caused generally by reactions to bumps, potholes, and roughnessencountered by the vehicle wheels during their interaction with the roadsurface. Thus the suspension springs and associated shock absorbersquell the harshness and movements being transmitted to the body/chassis.

The sway or side to side rolling motions that vehicles experience due tocornering forces, also cause vehicle springs to be loaded or unloaded,depending which way the vehicle is rolling during cornering. Manyvehicles have an anti-sway/roll bar installed to help the vehicle bodyresist the rolling actions. These devices help the vehicle partiallyresist roll but only as it relates to the body lean, because they arefixed to the sprung mass and leaning with the body. Thus, they canactually reduce the load on the unloaded side of the vehicle. They usethe body as a structure to support the torsion bar of the anti swaysystem transferring wheel jounce motion across to the opposite side. Thedisclosure herein will obviate the need for anti-sway bars, saving thecost of providing and installing them. Shock absorbers only dampen thebouncing movement of the vehicle wheels and suspension caused by thereaction to road surface, cornering and braking. Thus, the rate of swaymay be affected only to a minor degree.

A floating aluminum piston is placed between the fluid moving piston andthe end of the shock body. The floating piston has nitrogen gas behindit that is at a preset pressure. This piston is used in racing shocksand other lift type shocks to do two things, first to pressurize thefluid at all times and second to raise the vehicle ride height. It isnot practical to fill the entire shock body with fluid on both sides ofthe fluid piston. This ensures that as the fluid moving piston movesaway from the end of the cavity as it would during extension or“rebound” travel, it does not permit a vacuum to form behind the fluidpiston and sucking against the shock travel. It maintains a pressurefront against the fluid to ensure that it is induced to pass the fluidpiston during jounce travel. The fluid piston has holes in it to allowthe fluid to pass by it and flexible shims on both sides of the fluidpiston are adjusted in strength to set the resistance to flow throughthe piston during normal movement. Stiffer shims result in higherresistance to the fluid being compressed against them.

All this and the use of nitrogen pressure against the piston are typicalof existing shock absorber design. The basic tubular shock absorber iswell known to skilled artisans, and is a commodity and is disclosed innumerous patents. The typical shock absorber is designed to dampenmotion and with coil over springs adjust the ride height and/or springstiffness.

U.S. Pat. No. 2,160,541 has a paired spring suspension connected inseries to only support load and jounce with the added spring coupled inline with the main spring for increasing the effective spring constantat the extremes of suspension travel. The techniques disclosed in thevarious embodiments of '541 are in the nature of an overload spring thatengages and changes the spring constant at the extremes of wheel travel.There is no spring in '541 connected to specifically resist reboundforces due to diverging motion of the sprung weight to unsprung weight.The disclosure of '541 specifically states that the higher springconstant results in less flex (on page 2 column 1 at lines 6 to 8), “ .. . which opposes any tendency of the vehicle to overturn laterally whennegotiating a curve.” In each embodiment of '541 the springs act inunison to control primarily load and jounce and there is no teaching ofa particular connection to directly apply rebound reaction of unsprungweight to one of the springs. The graph in '541 showing wheel travelverses spring forces verifies these conclusions. U.S. Pat. No. 5,263,695discloses a refinement of the '541 teaching that includes a shockabsorber for damping motion and an elastic block to ameliorate thetransition between first and second springs for carrying the load. Inaddition to many disclosures in '695 of prior paired springconfigurations there is a specific explanation in column 5, lines 1through 5 as follows:

“The suspension according to the invention produces a comfort levelwhich is higher the more the transition from one stiffness to the othertakes place progressively (see the patents cited in the state of theart).”

The state of the art referred to includes prior patents of the sameinventor and the acknowledgements of those prior patents clearlyidentifies the teachings as merely two springs of different stiffness inseries. Even in FIG. 7 of '695 the springs are concentrically mountedbut act in series, see column 4, lines 8 through 12. At best thestructures for multiple springs shown in these patents have differingspring rates to give an allegedly more comfortable ride but do notspecifically disclose rebound control.

U.S. Pat. No. 3,830,517 is a motorcycle rear wheel spring suspensionwherein a top spring is longer and absorbs upward road shock and abottom spring absorbs the rider's weight. Nothing is disclosed aboutresisting rebound with either the top or bottom spring and no attachmentof the springs is shown or described that would operate to controlrebound of the sprung weight.

U.S. Pat. No. 3,049,359 has a pair of coaxial coil springs designed tomaintain ride height by automatic screw adjustment of the smaller andlighter inner tension coil spring. No disclosure of rebound control ofsprung weight is made and the inner tension coil spring loadings arevaried only in so far as the ride height is less or more than requiredas such the size and strength of the inner tension spring would beinsufficient to transfer the unsprung weight to the chassis and resistrebound. Moreover the working travel of both springs appears to be thesame; thus, no rebound control is possible.

No existing suspension system suspends the chassis and/or body betweenopposing springs to counter load and jounce and reaction and reboundalong different portions of the axle and wheel travel. An opposingspring suspension as disclosed herein can have little effect on the ridestiffness, but stabilizes cornering and evasive maneuvering sway byutilizing the unsprung weight of the axle system thus helping thevehicle to resist roll while maintaining the general ride quality.

U.S. Pat. No. 3,297,312 has a combination shock absorber and spring forautomobile suspensions. Close examination reveals that a main rodconnects between a top cap and a nut to bottom tube. It appears that therod will bottom out against the tube end when the springs are compressedbecause rod 52 is of set length and incompressible. The four springsstacked, as a unit, abut each other to act as one continuous variablerate spring. Specifically, the upper two springs have a disc thatseparates them that shifts up and down with the movement of the springs.The disc has valve holes in it to permit the movement of fluid to eachside of the disc to act as a shock absorber. This appears to haveminimal effect or use.

U.S. Pat. No. 5,183,285 has a suspension of a stiffness that is greaterbetween the operating load position and the suspended wheels positionthan between the operating load position and the collapsed position. Itis a suspension and a suspension process that uses a greater stiffnessin the region of “rebound” than in the region of “bump” with means forsmoothing the stiffness from the passage of one region to the other, andmeans for varying the reference position for “operating load” as afunction of the number of persons and the load in the vehicle. Asuspension wherein the stiffness is greater in the region between theposition “operating load” and a position “suspended wheels” than in therange between the position “operating load” and a position “collapsedsuspension” up to shock abutment. The suspension has stiffness greaterin the region of “rebound” than in the region of “bump”; if these aregraphically represented, a change of thickness represented by a break inthe slope appears. FIGS. 13, 14 and 16 in U.S. Pat. No. 5,183,285 have arebound spring around a shock positioned by a jack for varying thereference position for “operating load” as a function of the number ofpersons and the load in the vehicle. The jack varies the preloadposition so there is no gap between rebound and bump.

U.S. Pat. No. 6,273,441 has a load leaf spring suspension system with anelongated stabilizing spring mounted there above the axle. The addedspring communicates roll resistance to the vehicle axle at its topcenter section. Force is concurrently applied at the ends of thestabilizing spring to the leaf spring of the vehicle by shackles.Adjustment of the device is achieved by use of a plurality of mountingapertures for the shackles located at varying distances from the centerof the stabilizing spring thereby allowing for adjustment by the userfor desired performance characteristics. Further force adjustment isachieved with one or a combination of an optional axle spacer located atthe center section of the stabilizing spring to communicate with theaxle. This stabilizer system does not employ opposing spring technology.

An influence is delivered on the vehicle center of gravity by opposingspring. The center of gravity of the unsprung mass relative to thecenter of gravity of the sprung mass is affected during the corneringmaneuvers. Without a tension or opposing spring to “tether” the sprungmass to the unsprung mass the unsprung mass does not initially helpresist the movement upwards of the sprung mass. This resistance is bestappreciated in a vehicle with very heavy unsprung mass relative to alighter sprung mass during corn ring versus a vehicle with lightunsprung mass relative to a heavy sprung mass. The former is recognizedas undesirable and the latter is greatly preferred and sought after indesign of vehicles. Often the physical limits of the vehicle componentsdetermine the practical boundaries of the sprung weight to unsprungweight ratio. The disclosure herein has an approach to ameliorate thedynamics of that relationship.

U.S. Pat. No. 6,017,044 has as it's main thrust regulation of springrebound and bound. Vertical downward jacking-force characteristics ofthe front suspension is set to be stronger relatively with respect tovertical downward jacking-force characteristics of the rear suspensionduring cornering. This is achieved by two means. The first is the use ofa very strong bump rubber in FIG. 3 of U.S. Pat. No. 6,017,044 thatcomes into play at the extreme end of the front jounce travel. This bumprubber is not needed in our disclosure. Second, a short “spring” item inFIG. 4 of U.S. Pat. No. 6,017,044 is intended to help control “jack up”of the rear suspension occurring near the extreme end of the roll. Theworking distance traveled is very short.

U.S. Pat. No. 6,220,406 discloses a damper for reducing sway. Itdiscloses background on various types of shock absorbers used inconnection with motor vehicle suspension systems to absorb unwantedvibrations that occur during various driving conditions. To dampen theunwanted vibrations, shock absorbers are generally connected between thesprung portion (i.e., the vehicle body) and the unsprung portion (i.e.,the suspension) of the vehicle. A piston assembly is located within theworking chamber of the shock absorber and is connected to the body ofthe motor vehicle through a piston rod. Generally, the piston assemblyincludes a primary valve arranged to limit the flow of damping fluidwithin the working chamber when the shock absorber is compressed orextended. As such, the shock absorber is able to generate a dampingforce to smooth or dampen the vibrations transmitted from the suspensionto the vehicle body. Typically, these vibrations occur from forcesgenerated in a vertical direction between the vehicle body and thedriving surface.

The greater the degree to which the flow of damping fluid within theworking chamber is restricted across the piston assembly, the greaterthe damping forces that are generated by the shock absorber. It is alsopossible to implement a primary valve arrangement that produces onemagnitude of damping on the compression stroke, and a second magnitudeof damping on the rebound stroke. These different damping rates aretypically constant as varying the sizes of the compression and reboundbypass orifices produces them.

While these shock absorbers produce ride comfort levels ranging from“soft” to “firm,” few, if any, of the known shock absorbers producevarying degrees of damping in a passive manner. The shock absorbersystems in use are capable of producing varying degrees of dampingforce; typically achieve this through the use of active control systems.These systems generally react to the vertically generated forces placedupon the vehicle suspension.

Accordingly, in '406 a shock absorber that includes a primary dampingmechanism for counteracting the vertical forces placed upon the vehicle,and a secondary damping mechanism which is capable of providing varyingdamping in response to horizontal and lateral forces that are placedupon the vehicle suspension. Secondary and variable damping is providedin proportion to the lateral force encountered by a passive control orvalves arranged to implement a passive anti-roll system for enhancingthe control to the vehicle provided by the vehicle suspension. Whilesuch a passive damping system also eliminates the need for complicatedand expensive controls to actively provide the varying degrees ofdamping, it is not easily adapted to the large variety of vehicles andtheir suspensions.

The problem of the lateral forces placed upon the vehicle suspension isthey are generated during high-speed cornering. As the suspension andtires counteract these lateral forces, a rolling action on the vehiclebody is produced. When these rolling forces exceed the limit for thevehicle, a rollover condition may be created wherein the vehicle isliterally flipped over on its side. Accordingly, it is desirable toprovide a shock absorber that provides increased resistance in responseto these lateral and horizontal forces for counteracting or at leastminimizing these rolling forces and the lift associated therewith.

BRIEF SUMMARY OF THE INVENTION

In the disclosed device and method, a rebound spring is placed to resistthe lengthening of the shock absorber from a position that starts oneinch into jounce travel from normal ride height to the full reboundsuspension travel position. This rebound spring is opposing andresisting the forces that are generated when the suspension is unloadingas for example during cornering. Namely the forces caused by the vehiclesuspension spring trying to return to its free position and thecentrifugal forces naturally resulting during cornering.

Using an additional coil spring mounted about the shock absorber toresist the rebound motion of the sprung weight applied by movementthereof away from the design height reduces chassis roll. The shockabsorber thus reduces the initiation of rebound travel between thesprung and unsprung weights as the vehicle becomes lighter due todynamic forces inducing roll or lift of the chassis and vehicle body.

The transitory effects of body roll during cornering flex the loadsprings on the side of the vehicle following the outside of the turn dueto increased transfer weight to that side. Meanwhile the springs on theside of the vehicle, following the inside of the turn, unload extendingtoward their free position using the axle as a location for inducinglift of the sprung weight on that side resulting in increased body roll.Roll or sway during sudden cornering or evasive maneuvers rotates thevehicle and its center of gravity “CG” around the Roll Center axis.

The Roll Center axis is a function of the particular vehicle'ssuspension geometry. Roll or sway is increased if the vehicle center ofgravity is raised as in a SUV, four-wheel drive vehicle or truck. Asudden turn opposite the direction of vehicle travel can cause momentumto continue the sway of the vehicle forcing its center of gravity tomove laterally past its maximum upright position, and so the vehiclecontinues on rolling and overturns.

The solution, as disclosed herein, may include an added rebound springmounted coaxial about the shock absorber tube to act primarily to resistrebound of the suspension from the design height position and therebyapply resistive force to the chassis via the shock absorber to reducelift. The coil rebound spring can also be added to a strut typesuspension for exactly the same purpose. It is an advantage of thepresent invention that it can be easily and inexpensively added as anafter market supplement to either the front or rear of an existingvehicle suspension with tubular shock absorbers. It is a furtheradvantage of the present invention that the coil rebound spring has verylittle influence on ride height and/or ride stiffness.

The coil rebound spring works from one inch of jounce travel all the wayto full rebound travel of the shock absorber. It works to prevent theonset of roll from the design height, rather than limiting the roll to acertain amount after it has rolled a certain amount. Limiting the rollfrom the design height position serves to reduce the momentum orinertial weight gain that occurs at the initiation of roll and continuesafter roll has begun. In other words, we seek to eliminate as much rollas possible from the outset. Rebound control overlaps the jouncecontrol; therefore the disclosed system is truly bi-linear, a preferredembodiment.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a side view in cross section of a shock absorber having a coilrebound spring thereabout.

FIG. 2 is a schematic perspective view of a vehicle rounding a cornerwith roll depicted about its longitudinal axis A—A.

FIG. 3 is a side view in cross section of a typical combined shockabsorber and strut type suspension unit, having a load spring but withthe addition of the disclosed coil rebound spring thereabout.

FIG. 4 is a graph showing the travel relative to the jounce and reboundloads of the combined shock absorber and strut depicted in FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a cross section view of a vehicle rebound control shockabsorber 10 with a special suspension coil rebound spring 11arrangement. It is to be used to replace a standard shock absorberinstallation independent of the vehicle spring system, as is commonlyfound in both vehicles with leaf type and coil type suspension springsystems. Commonly a shock absorber connects the sprung mass to theun-sprung mass and is used only to dampen unsprung mass oscillationsinduced by bumpy roads and sometimes with helper load springs forpreloaded height and jounce improvement. The sprung mass is carried onvehicle chassis and body and herein after will be referred tostructurally as chassis 16. The unsprung weight is that which is notsupported by the vehicle suspension spring system, i.e. axles 15,wheels, tires, brake assemblies and suspension components that hangdownwardly if the body is lifted. Typically, the passenger vehicle hasfour wheels with associated suspension with two at the front and two atthe rear. The disclosure herein is to cover any number of axle 15 andwheel combinations so long as there is roll to be restrained.

FIG. 1 shows a coil spring mounted about a rebound control shockabsorber 10 for exerting force to resist upper rebound control shockabsorber 10 movement from the normal design height or preloaded rideposition of chassis 16. When both ends of the rebound control shockabsorber 10 are pulled apart, as experienced by chassis 16 when it liftsduring rebound of the axle 15. It is called coil rebound spring 11because it is intended to counter the lifting action of the vehiclesuspension during roll due to cornering maneuvers. When a vehiclecorners, its chassis 16 rolls about its longitudinal axis A—A in FIG. 2relative to axles 15. Load carrying coil springs 14 on the outside ofchassis 16 become compressed as they assume jounce and the coil loadsprings 14 located on the inside of the turning chassis 16 duringcornering become extended while experiencing rebound see FIG. 2. Coilload springs 14 on the unloading inside side of the cornering vehicleare trying to return to their free state as they extend. Thus coil loadsprings 14 as they extend exert a lifting force to chassis 16 which isexacerbating the roll angle of the body mass. The lifting force isexactly what is not desired and is resisted by the coil rebound springs11 herein disclosed. The whole purpose of using coil rebound springs 11is to reduce chassis 16 roll at initiation of and during corneringbecause rebound movement at any axle 15 will likewise be resisted.

FIG. 3 shows another rebound control shock absorber 10 having coilrebound spring 11 thereabout, but with the addition of a compressiontype suspension coil load spring 14. The additional compression coilload spring 14 carries the sprung weight and is intended to replace orsupplement chassis 16 existing original equipment manufacturersuspension load spring 14, if any. If load spring 14 is carried on therebound control shock absorber 10 and no separate load spring 14 is usedthe vehicle suspension would be fully self-contained. Thus the reboundcontrol shock absorber 10 with an integral coil load spring 14 as perFIG. 3 would be able to serve as a replacement assembly providing thatthe vehicle mounting points for such an assembly is sufficient torespond and carry the loadings expected. Typically, strut mountings thatare prevalent on modern cars and trucks are adequate for operation withthe assembly shown in FIG. 3. It is important to note that coil reboundspring 11 seeks to control the sprung weight and the coil load spring 14if original equipment manufacturer and/or on the rebound control shockabsorber 10 as in FIG. 3 supports the sprung weight.

A rebound control shock absorber 10 for placement between axle 15 andchassis 16 is shown in FIGS. 1, 2 and 3. The rebound control shockabsorber 10 is for additionally controlling the vehicle dynamics withincreasing resistance under motion between a preloaded vehicle rideheight position to a fully extended position of rebound control shockabsorber 10 during rebound movement of chassis 16 away from axle 15along an axis B—B through the rebound control shock absorber 10. It isrebound control shock absorber 10 that applies the unsprung weight ofthe wheels, brake and axle 15 to chassis 16 through coil rebound spring11. The goal is not to lift the axle, wheel and its tire from theground, if possible, during cornering but to apply the unsprung weightof those components at the lifting side of chassis 16 to resist roll ofthe chassis and body.

An axle mount 17 on axle 15 is provided to connect to rebound controlshock absorber 10. A chassis attachment 18 on chassis 16 of the vehicleconnects to the depending rebound control shock absorber 10 so that itmay operate along axis B—B between axle mount 17 and chassis attachment18. An elongated rod 19 has opposite ends 20 and 21 carried and alignedalong the axis B—B. End 20 connects to chassis attachment 18 in FIG. 1or 3. While rebound control shock absorber 10 is shown with elongatedrod 19 and end 20 at the top in FIGS. 1 and 3, skilled artisans willunderstand that it can be inverted so that elongated rod 19 connects toaxle mount 17. A fluid displacement piston 22 is located on end 21. Ifrebound control shock absorber 10 is inverted (not shown) then attentionto how coil rebound spring 11 carries the unsprung weight must beaddressed; again this is within the skill of artisans. Fluiddisplacement piston 22 is carried on the elongated rod 19 opposite itsconnection end 20. Likewise a tube 23 is aligned along the axis B—B andconnects to the axle mount 17 when the end 20 is connected to thechassis attachment 18; alternatively, the tube 23 connects to chassisattachment 18 when the end 20 is connected to the axle mount 17.

Tube 23 has inside and outside cylindrical surfaces 24 and 25. Insidecylindrical surface 24 is sized diametrically for surrounding the fluiddisplacement piston 22 for sliding sealing circumferential engagementthere between with reciprocation along the axis B—B. A chamber 26 isdefined by the inside cylindrical surface 24 and chamber 26 carriesdamping fluid (not shown) about fluid displacement piston 22 forcontrolled resistance to sliding reciprocal movement of the fluiddisplacement piston 22 within tube 23 against the inside cylindricalsurface 24 and along the axis B—B.

Coil rebound spring 11 is carried about outside cylindrical surface 25of tube 23 coaxial thereto and for expansion and contraction along theaxis B—B as in FIGS. 1 and 3. Coil rebound spring 11 is mounted torestrain expansion along the axis B—B of the rebound control shockabsorber 10 between axle 15 and chassis 16 of the vehicle. Restraint isfrom at least the preloaded vehicle ride height position to the coilrebound spring 11 fully extended position during rebound motion of theaxle 15 away from the chassis 16 as in FIG. 2.

Tub 23 is elongated along the axis B—B with a top 27 and a bottom 28separated from each other. A flanged retainer 29 affixes about theoutside cylindrical surface 25 of tube 23. Flanged retainer 29 islocated between the top 27 and bottom 28 for applying axial reboundloads to tube 23 from rebound spring 11 during motion along axis B—B ofthe axle 15 away from chassis 16. A tube cap 30 mounts in the top 27 andextends from tube 23 to a seat 31 overhanging tube cap radially from theoutside cylindrical surface 25 as shown in FIGS. 1 and 3.

A bore 32 positioned in and passing through tube cap 30 is coaxial withaxis B—B and bore 32 allows elongated rod 19 to pass there through andreciprocate therein. Tube cap 30 connects axially to tube top 27 tocapture coil rebound spring 11 between flanged retainer 29 and seat 31.The coil rebound spring is thereby supported for coaxiallycircumscribing tube 23 between top 27 and bottom 28 thereof. Rebound isresisted during expansion of rebound control shock absorber 10 from itspreloaded height to full extension along the axis B—B with motion ofaxle 15 away from chassis 16.

A cylindrical housing 33 in FIGS. 1 and 3 is affixed to the end 20connected to either chassis 16 or axle 15 depending on the orientationof rebound control shock absorber 10. Cylindrical housing 33 extendsfrom its affixed connection along the axis B—B to engage flangedretainer 29. Cylindrical housing 33 has a circular cross section sizeddiametrically for surrounding coil rebound spring 11 with a clearancethere between. In FIG. 3 the cylindrical housing 33 is shown withexternal threads. A fastener 34 on tube cap 30 adjacent seat 31 isshaped to retain coil rebound spring 11 to seat 31 during movement ofcoil rebound spring 11 along the axis B—B with motion of axle 15 awayfrom chassis 16. The coil rebound spring 11 is preloaded by the flangedretainer when the coil rebound spring is captured between flangedretainer 29 and seat 31. During expansion of the rebound control shockabsorber 10 from its preloaded position, the coil rebound spring resistsexpansion under motion of axle 15 away from chassis 16.

Coil load spring 14 mounts co-axially about cylindrical housing 33 forcarrying chassis 16 of the vehicle from the preloaded ride heightposition to a full jounce position compressing the coil load spring 14as shown graphically in FIG. 2. An upper collar 35 about cylindricalhousing 33 is near connection end 20 and a lower collar 36 at tubebottom 28 capture coil load spring 14 so rebound spring 11 substantiallyresists expansion after coil load spring 14 substantially resistscompression during rebound and jounce, respectively. The term, “after”is used in the preceding sentence because rebound spring 11 and coilload spring 14 operate independently to control (resist) differentloads.

A method for rebound control by rebound control shock absorber 10 placedbetween axle 15 and chassis 16 of a vehicle is operable at least betweena preloaded vehicle ride height position to a fully extended positionduring rebound movement of axle 15 away from chassis 16 along axis B—B.The method of rebound control has the steps of mounting rebound controlshock absorber 10 to axle mount 17, and attaching rebound control shockabsorber 10 to chassis attachment 18 along axis B—B there between.Another step connects elongated rod 19 having opposite ends 20 and 21 soend 20 connects to either axle mount 17 or chassis attachment 18.Locating piston 22 at the opposite end and connecting tube 23 to axlemount 17 if the elongated rod 19 is connected to chassis attachment 18or connecting tube 23 to chassis attachment 18 if the elongated rod 19is connected to the axle mount 17 are steps. The step of sizing tube 23with a cross section to surround piston 22 for sliding sealingcircumferential engagement within tube 23 due to motion of axle 15 awayfrom chassis 16 is performed. Carrying damping fluid about piston 22 inchamber 26 defined by tube 23 is a step. The steps of controllingresistance to sliding reciprocal movement of piston 22 in tube 23 withthe damping fluid, and carrying rebound spring 11 about tube 23 forrestraining expansion of the rebound control shock absorber 10.Restraining is between axle 15 and chassis 16 of the vehicle from thepreloaded vehicle ride height position to the fully extend positionalong the axis B—B during rebound movement of axle 15 away from chassis16 are followed.

The step of supporting rebound spring 11 coaxially circumscribing tube23 so that rebound is resisted during expansion of rebound control shockabsorber 10 from its preloaded height to full extension along the axisB—B with motion of axle 15 away from chassis 16 is done. The step ofsupporting load spring 14 relative to rebound spring 11 coaxial to oneanother and along the axis B—B with a clearance there between occurs.During expansion of rebound control shock absorber 10 from its preloadedvehicle height to full extension along the axis B—B there is motion ofaxle 15 away from chassis 16 load spring 14 and the rebound spring 11operate substantially independent of one another to resist jounce andrebound, respectively. The method for rebound control by rebound controlshock absorber 10 with the step of supporting rebound spring 11 and loadspring 14 at the preloaded vehicle height so that the working forceapplication travel there between is overlapping. Thus, about one inch oftravel overlap during movement of the rebound spring 11 along the axisB—B with motion of axle 15 away from chassis 16 from the preloadedvehicle height is thus preformed. FIG. 4 shows in graphic form theresultant of overlap for rebound spring 11 and the load spring 14combined. In the graph of FIG. 4 the load paths at a rate of 320 poundper inch compression jounce spring and a rate of 160 pounds per inchrebound counter spring are shown. The affect on the rebound travelspring of the suspension if engaged at one inch of jounce is no curve atthe transition point.

The step of having the ratio of the spring constants of coil reboundspring 11 to the spring constant of load spring 14 be less than one. Sothat during expansion of rebound control shock absorber 10 from itspreloaded position coil rebound spring 11 happens to resist expansionunder motion of axle 15 away from chassis 16 to a lesser extent thanload spring 14 resists jounce. The step of coil rebound spring 11applying force to resist rebound of the axle 15 occurs.

The method for rebound control by rebound control shock absorber 10 hasthe step of locating coil rebound spring 11 to substantially resistexpansion of rebound control shock absorber 10. The step of co-axiallypositioning coil load spring 14 to substantially resist compression ofrebound control shock absorber 10 during rebound and jounce is performedindependently.

While the examples illustrating rebound control shock absorber 10 andrebound spring 11 are disclosed and described, skilled artisans willappreciate that many variations for the addition of rebound spring 11will be possible. The specific examples should not be consideredlimiting and the particular arrangements shown in FIGS. 1 and 2 aremerely for depiction of but some examples of form. In that regard, inthe claims that follow the orientation of rebound control shock absorber10 is either up or down and angled mounting thereof is also within thescope of the claims.

What is claimed is:
 1. A rebound control shock absorber for placementbetween an axle and a chassis of a vehicle, the rebound control shockabsorber for additionally controlling the vehicle dynamics withincreasing resistance under motion between a preloaded vehicle rideheight position to a fully extended position during rebound movement ofthe chassis away from the axle along an axis through the rebound controlshock absorber, the rebound control shock absorber comprising: a) anaxle mount on the axle of the vehicle and a chassis attachment on thechassis; b) an elongated rod having opposite ends aligned along theaxis, the elongated rod connected by one end to either the axle mount orthe chassis attachment; c) a fluid displacement piston located on theend opposite to the one end, the fluid displacement piston carried onthe elongated rod opposite the one end; d) a tube aligned along the axisand connected to the axle mount if the one end is connected to thechassis attachment or to the chassis attachment if the one end isconnected to the axle mount, the tube having inside and outsidecylindrical surfaces, the inside cylindrical surface sized diametricallyfor surrounding the fluid displacement piston for sliding sealingcircumferential engagement there between and for reciprocation along theaxis; e) a chamber defined within the inside cylindrical surface, thechamber carrying damping fluid about the fluid displacement piston forcontrolled resistance to sliding reciprocal movement of the fluiddisplacement piston within the tube against the inside cylindricalsurface and along the axis; f) a coil rebound spring carried about theoutside cylindrical surface of the tube coaxial to and for expansion andcontraction along the axis, the coil rebound spring mounted to restrainexpansion along the axis of the rebound control shock absorber betweenthe axle and the chassis from at least the preloaded vehicle ride heightposition to the fully extended position during rebound motion of thechassis away from the axle; g) a flanged retainer affixed about theoutside cylindrical surface of the tube, located between a top and abottom of the tube and affixed for applying axial rebound loads to thetube from the coil rebound spring during motion of the chassis away fromthe axle; h) a tube cap mounted in the top and extending from the tubeinside cylindrical surface to a seat radially overhanging the tube capbeyond the outside cylindrical surface, and i) a bore passing throughthe tube cap positioned along the axis allows the elongated rod to passthere through and reciprocate therein, the tube cap connecting axiallyto the tube top to capture the coil rebound spring between the flangedretainer and the seat, the coil rebound spring thereby supported forcoaxially circumscribing the tube so that rebound is resisted duringexpansion of the rebound control shock absorber from at least apreloaded height to full extension along the axis with motion of thechassis away from the axle.
 2. The rebound control shock absorber ofclaim 1 further comprising a cylindrical housing affixed to the one end,the cylindrical housing extending from the one end along the axis toengage the flanged retainer, the cylindrical housing having a circularcross section sized diametrically for surrounding the coil reboundspring with a clearance there between.
 3. The rebound control shockabsorber of claim 2 wherein the coil rebound spring is preloaded by theflanged retainer when the coil rebound spring is captured between theflanged retainer and the seat so that during expansion of the reboundcontrol shock absorber from its preloaded position the coil reboundspring resists expansion under motion of the chassis away from the axle.4. The rebound control shock absorber of claim 2 wherein a coil loadspring mounts co-axially about the cylindrical housing for carrying thechassis of the vehicle from the preloaded ride height position to a fulljounce position while compressing the coil load spring.
 5. The reboundcontrol shock absorber of claim 4 wherein an upper collar about thecylindrical housing near the one end and a lower collar about the tubecaptures the coil load spring so that the coil rebound springsubstantially resists expansion and the coil load spring substantiallyresists compression during rebound and jounce respectively.
 6. Therebound control shock absorber of claim 1 further comprising a fasteneron the tube cap adjacent the seat for retaining the coil rebound springto the seat during movement of the coil rebound spring along the axiswith motion of the chassis away from the axle.